The general aim of this project is to obtain a more precise understanding of the role of multiple factors possibly related to the pathogenesis of multiple sclerosis. (1) Determination of histocompatibility types in a carefully selected population of MS patients and appropriate controls. (2) Correlation of histocompatibility data in both the patients and controls to the humoral and cell-mediated immune response to viruses. (3) Evaluation of cerebrospinal fluid immunoglobulin content and specificity. (4) Evaluation of families with a multiple incidence in multiple sclerosis and examination of affected and nonaffected members of these families with respect to the above. (5) Identification of additional lymphocyte antigens which may show a greater degree of correlation with multiple sclerosis than presently identified lymphocyte antigens. Similar studies are being conducted in patients with SSPE and neuromuscular diseases. BIBLIOGRAPHICAL REFERENCE: McFarlin, D.E. and McFarland, H.F.: Histocompatibility studies and multiple sclerosis. Arch. Neurol. 33:395-398, 1976.